Cthulhu Macrofasciculumque n. g., n. sp. and Cthylla Microfasciculumque n. g., n. sp., a Newly Identified Lineage of Parabasalian Termite Symbionts

Erick R James,Patrick J Keeling,Noriko Okamoto,Fabien Burki,Rudolf H Scheffrahn,Jonathan H Badger

doi:10.1371/journal.pone.0058509

Erick R James, Patrick J Keeling + Show 4 more

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https://doi.org/10.1371/journal.pone.0058509

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Abstract

The parabasalian symbionts of lower termite hindgut communities are well-known for their large size and structural complexity. The most complex forms evolved multiple times independently from smaller and simpler flagellates, but we know little of the diversity of these small flagellates or their phylogenetic relationships to more complex lineages. To understand the true diversity of Parabasalia and how their unique cellular complexity arose, more data from smaller and simpler flagellates are needed. Here, we describe two new genera of small-to-intermediate size and complexity, represented by the type species Cthulhu macrofasciculumque and Cthylla microfasciculumque from Prorhinotermes simplex and Reticulitermes virginicus, respectively (both hosts confirmed by DNA barcoding). Both genera have a single anterior nucleus embeded in a robust protruding axostyle, and an anterior bundle flagella (and likely a single posterior flagellum) that emerge slightly subanteriorly and have a distinctive beat pattern. Cthulhu is relatively large and has a distinctive bundle of over 20 flagella whereas Cthylla is smaller, has only 5 anterior flagella and closely resembles several other parababsalian genera. Molecular phylogenies based on small subunit ribosomal RNA (SSU rRNA) show both genera are related to previously unidentified environmental sequences from other termites (possibly from members of the Tricercomitidae), which all branch as sisters to the Hexamastigitae. Altogether, Cthulhu likely represents another independent origin of relatively high cellular complexity within parabasalia, and points to the need for molecular characterization of other key taxa, such as Tricercomitus.

Highlights

The hindgut of lower termites has long been known for the diversity of its community of symbiotic protists [1]
The community is dominated by Parabasalia, which are of interest due to the critical ecological role they play in the breakdown of lignocellulose, and because these symbionts have evolved a remarkable range of sizes and structural complexities [2]
The likelihood that many, if not most, of the major types of large hypermastigtes have been described is supported by phylogenetic analysis of molecular surveys of hindgut diversity: there are many lineages in the tree of parabasalians that are made up entirely of ‘‘unidentified environmental sequences’’ from termite hindguts [9], but only a few of these are likely to represent organisms of large size and substantial complexity

Summary

Introduction

The hindgut of lower termites has long been known for the diversity of its community of symbiotic protists [1]. We describe Cthulhu macrofasciculumque found in Prorhinotermes simplex (Hagan), and Cthylla microfasciculumque, found in Reticulitermes virginicus (Banks), newly described genera and type species of relatively small parabasalian termite symbionts that address both these issues.

Results

Conclusion